Cutting concrete patio?

[trader4]

Here's the situation. I have a stamped concrete patio where the concrete apparently was not finished off with the proper consisten pitch so that water will drain. There are two areas where pools of water remain after the rain. Both of these happen to be in areas where there are relief cuts in the concrete. It appears that these cuts only go about half way through the concrete. Which makes sense I guess, since for the purpose of relief cuts that is sufficient.

So, my idea is to cut them the rest of the way through in the area of the puddles so the water can then drain. I'm thinking about 10 ft or so is all I need in total and I'm thinking about using a circular saw with either a diamond blade or else one of those abrasive saw blades that also say they will cut concrete. The difference is the diamond blade is $40, while the abrasive ones are $6. I obviously don't care if it takes a bit longer with the abrasive blade, but I don't want to have to go through 4 blades and have it take 3 hours either. I think we can assume the remaining concrete is about 2" thick.

Any thoughts? Anyone do anything similar with one of the abrasive type blades? Thanks.

[Vic Smith]

I cut a number of pavers - all the way through - with an abrasive blade. You could see it wore down about an inch. Old 6 1/2" saw. Hard to say, but a guess is you might need 4-6 blades to do 10' by 2". How about drilling some holes instead?

[Home Guy]

Why don't you drill a few 1/4" holes through the concrete in the relief cuts instead ?

Use a long drill so the water will more easily / quickly be absorbed in the ground under the slab.

Unless there's a lot of water that pools on the slab - or you're impatient about how long it takes for the water to drain, then one (or a few) small holes should suffice.

[Jim Elbrecht]

I don't think that's a good idea. If it *does* drain, you'll get scouring under the slab-- or you could get muddy water coming *up* when it rains.

Not to mention that all the re-wire or rod, if they used it, is below that cut and you don't want to cut it--- nor will either the diamond blades, nor the abrasive ones that I've used, react well to the iron.

I'd be inclined to widen them if they end someplace that can take the runoff.

I got 3 wet/dry diamond blades off ebay for about $30 [free shipping] many years ago. The first one cut a 2" slab for 60' & was looking good until I tried another slab with a re-rod in it. It stopped and died at the iron. The second one, I adjusted so it didn't hit iron and it is still in that old B&D that I abuse with such shenanigans. I've cut a pile of block, brick, concrete and stones with it.

I trickle water in front of the cut so I'm dealing with mud instead of dust. I've never even tripped the GFCI.

HF has the blades for $20--

I've never had an abrasive blade that would last 1/20th the amount of the diamond blades--- and they throw off a whole lot more stink & dust. Maybe they're better these days. I haven't bought one in

4-5 years.

Jim

[DD_BobK]

Get the diamond blade.

I bought my first diamond blade (6-1/2") nearly 30 years ago & have gotten great use out of it. In those days they were pretty spendy.

SInce then I've picked up various diamond blades for 4-1/2 grinder. Hilti, Bosch & Dewalt.

My experience with concrete abrasive blades has been disappointing. The blades wear quickly, cut depth thus varies and I wound up making multiple passes (with multiple blades) to get a consistent cut depth.

cheers Bob

[DD_BobK]

I would ditto Jim's advance & experience, except.......

the diamond blades that I have used that were rated for cutting reinforced concrete made short work of the occasional piece of rebar. The same goes for wet cut Hilti diamond core bit. Somewhere kicking around little chunks of #9 bars that cut partially severed with a Hilti core bit.

cheers Bob